1. Field of the Invention
The present invention relates to the art of key cases and particularly to those key cases used in prisons for security purposes which cover only a portion of the key.
In prisons, it is important that a prisoner not be allowed to see the tumbler cuts on cell keys. If the tumbler cuts are exposed, the prisoner may try to duplicate the key or tamper with the cell lock. A key case which shields the tumbler cuts can, therefore, make an important contribution to overall prison security.
Nonetheless, a tumbler cut key shield must also be convenient and workable for the prison guard. It should easily retract to expose the tumbler cuts when the lock must be used but then automatically return to re-cover the tumbler cuts when the key is no longer needed. The key shield should be of sturdy construction with a minimum of parts to withstand the rough prison environment and yet be inexpensive. Also the key shield should not interfere with the free interchangeability of prison keys between key rings nor should it block out any serial numbers that are stamped on the key.
2. Description of the Prior Art
Key cases of various types have long been known. The inventors are aware, for instance, of several patents in which a key is held inside a case by a button pin. In each of these patents, the case is at least large enough to cover the entire key and, in some instances, it can completely cover several keys. The neck of the button pin is channeled into a longitudinal slot in the case which allows the key to be exposed and retracted by pushing the button portion of the pin back and forth within the longitudinal slot. U.S. Pat. Nos. 1,924,134 (H.R. Segal), 1,934,889 (H.R. Segal), 1,974,547 (A.R. Slade), 2,180,717 (E.C. Nelson), 2,270,621 (R. C. Brugnoni) and 2,509,318 (A. Segui, Jr.) disclose such key cases. These key cases have the drawback of being bulky in comparison to the size of the key. Unlike the present invention, the key and key case cannot be conveniently placed on or interchanged between key rings. Using such key cases, a prison guard would not be able to carry the usual 30 or more keys on a key ring attached to his belt. These key cases are also more difficult to operate than the present invention. One must push on the button pin to expose the key and then remember to pull back on the button to retract the key. Using the present invention, one can expose the key tumbler cuts merely by pushing the key against the lock opening, and the shield falls back to re-cover the tumbler cuts after use merely by letting the key hang from a key ring. The present invention achieves an economy of space and simplicity of use unknown in the slotted key case prior art.
A spring loaded key shield manufactured by the Folger Adam Company of Joliet, Illinois has recently been used in prisons to hide the tumbler cuts of keys. The Folger Adam shield covers only the tumbler cut half of the key and is anchored by a pin placed through the key at a point near the center of the key's faces. The Folger Adam shield swings laterally away from the key when the key is in use and then the spring snaps it back when the key is pulled away from the lock. Serious maintenance difficulties have been created by the use of a spring on the Folger Adam shield. The springs will often bend, rust or break. Sometimes the anchoring pin must be drilled out to replace a broken spring. The Folger Adam shield has also been awkward to use because the spring pressure causes the shield to press against the lock and interfere with turning the key to unlock the door.
The present invention is a simpler, less expensive device which eliminates the difficulties associated with spring loading. The only moving part of the present invention is the shield itself. There is very little that can go wrong with the present invention regardless of the treatment it receives. The shield on the present invention also moves straight back so as not to interfere with the key turning operation. The present invention overcomes the disadvantages of the prior art to create a durable, inexpensive and practical key shield.